1. Field of the Invention
The present invention relates to a clutch device for transmitting the motive power from an associated follower pulley to a selected reel support via an associated idler gear in a videotape recorder.
2. Related Arts
In the videotape recorder rotation of the capstan motor is transmitted to the reel gear of a selected reel support via the clutch device. The primary pulley is fixed to the shaft of the capstan motor, and the follower pulley of the clutch device is connected to the primary pulley by the belt.
The videotape recorder is loaded with the magnetic tape. Specifically the magnetic tape is pulled out from the cassette to be pinched between: the pinch roll and the capstan. The videotape recorder can work in: the forward play mode in which the winding reel support is rotated to wind the magnetic tape therearound while the magnetic tape is played back; the reversal play mode in which the unwinding reel support is rotated to wind the magnetic tape therearound while the magnetic tape is played back; the fast feeding mode in which the winding reel support is rotated fast to wind the magnetic tape therearound quickly; and the rewinding mode in which the unwinding reel support is rotated fast to wind the magnetic tape therearound quickly.
Both in the forward play mode and in the reversal play mode the small clutch gear is meshed with the large idler gear, allowing the capstan motor to transmit its rotation from the follower pulley to the large idler gear via the friction type of power-transmission. In contrast with this, both in the fast feeding mode and in the rewinding mode the large clutch gear is engaged with the small idler gear, and the follower pulley is engaged directly with the clutch, thereby allowing the capstan motor to transmit its rotation from the follower pulley to the small idler gear via the large clutch gear.
Referring to FIG. 7, the small clutch gear of the coupling gear unit 1 is engaged with the large idler gear 15 when the videotape recorder is in the forward play mode. As shown in the drawing, the coupling gear unit 1 is raised by the coiled spring 16 so that the small clutch gear of the coupling gear unit 1 may be engaged with the large idler gear 15. When the videotape recorder is in the fast feeding mode or in the tape rewinding mode the coupling gear unit 1 is pushed down with an associated lever, allowing the large clutch gear to mesh the small idler gear. Thus, the reel support is rotated at an increased speed.
In the play mode and the reversal play mode the selected clutch gear of the coupling gear unit 1 is meshed with the counter idler gear 15 to transmit the rotary torque to the reel support. The gear teeth have tapered surfaces for reducing stick of teeth in mold. What with the tapered surfaces of gear teeth and what with the counter force caused by the transmitted torque the clutch and idler gears meshed together cannot be stable in position. In the worst incident the clutch and idler gears come off from each other. Even though these gears remain in their meshing condition, they are climbing up or down on each other all the time, chattering ceaselessly.
One object of the present invention is to provide an improved clutch device for transmitting the motive power from an associated follower pulley to a selected reel support via an associated idler gear in a videotape recorder, assuring that the clutch and idler gears do not come off from each other, and that these gears do not climb up or down on each other, not chattering.
To attain this object a clutch device for transmitting the motive power from an associated follower pulley to a selected reel support via an associated idler gear in a videotape recorder, is improved according to the present invention in that it comprises a top clutch fixed to the top of the axle of the follower pulley, said top clutch having a plurality of nail pieces integrally connected to and descending from its circumference, each nail piece having two ramp-shaped indents formed on its opposite sides; and a coupling gear urged by an associated coiled spring apart from the top clutch and fitted around the top clutch, said coupling gear having rib pieces integrally connected to and descending from its circumference, each rib piece having two ramp-shaped indents formed on its opposite sides, thereby allowing one or the other ramp-shaped indent of each nail piece to engage with the counter ramp-shaped indent of each rib piece while the top clutch is made to descend in the annular space of the coupling gear, thus preventing further descent of said top clutch.
The two ramp-shaped indents of each rib piece are present at different levels.
Other objects and advantages of the present invention will be understood from the following description of a clutch device according to one preferred embodiment of the present invention: